A New Study Links Smoking Weed With a Loss in Verbal Memory

Like smoking pot? A new study published online by JAMA Internal Medicine has some bad news. The study, conducted by Wayne Hall of the Center for Youth Substance Abuse Research at the University of Queensland in Australia, and Michael Lynskey of the National Addiction Centre at King’s College London found that individuals who smoke marijuana regularly in their teenage years experience a loss in verbal skills in middle age.

According to a report on CNN.com, the study queried over 5, 000 participants aged 18 to 30 about their weed use and it tested participants’ cognitive skills using standardized tests of verbal memory, processing speed and executive function.

To complete their work, researchers followed up with participants at various points over a 25-year span. At the end of 25 years some participants had dropped out of the study but 3,400 individuals were still involved, giving researchers a good base for their conclusions.

And conclusions they made. Researchers found that for those individuals who were current marijuana smokers, they generally had poorer verbal memory and slower processing speeds.

People with a lifetime of exposure to marijuana generally had poorer performance in all areas the study tested: verbal memory, processing speed and executive function.

Surprisingly, for every five years of past marijuana exposure, 50% of participants remembered one word fewer from a list of 15 words.

But was it a case of better or lesser education? Apparently not.

“In this study, there are as much women as men, as much black as white, as much lower education as higher education,” said Dr. Reto Auer, one of the study’s authors. “It provides a better sense of what the association is in the overall population.”

With the recent legalization of marijuana sales in certain US states, more questions are being raised about the medical effects of long-term use of the drug.

“The public health challenge is to find effective ways to inform young people who use, or are considering using, marijuana about the cognitive and other risks of long-term daily use,” wrote study authors Hall and Lynskey. “More research on how young people interpret evidence of harm from marijuana and other drugs would be useful in designing more effective health advice.”